1. Field of the Invention
The invention relates to lancet injectors and more particularly to lancet injectors having lancet tips that are automatically removable from the lancet injector without requiring hand contact with the lancet.
2. Description of Related Art
Lancets are used to pierce the skin of a subject, usually through the finger. Blood then flows through the incision where it can be collected for testing in a blood collection tube such as a capillary tube or pipette.
Historically, early lancets generally had a handle and a needle extending therefrom. However, numerous problems are inherent with such lancets such as controlling the depth and angle of penetration by the needle, controlling the force of the insertion, and the psychological affect to the user of seeing the exposed needle.
One attempt to avoid these and other problems with this early type of lancet was to create lancets having needles that are spring loaded to be injected into and removed from the subject's skin. Typically, these devices hide the needle both before and after the incision is made to prevent its view by the subject and to prevent inadvertent contact with the needle. An example of such a lancet injector is disclosed in U.S. Pat. No. 4,580,565 issued on Apr. 8, 1986 to W. D. Cornell and C. Evans and its parent application U.S. Pat. No. 4,503,856, issued to W. D. Cornell and C. Evans on Mar. 12, 1985, both assigned to the assignee of the present application.
The invention disclosed herein is an improvement of the lancet injector described in these two patents. Consequently, in order to better understand the present invention, a verbatim detailed description and FIGS. 1-6 of the lancet injector of the two above-referenced patents are set out herein in their entirety:
"Referring now to the drawings and particularly to FIGS. 1 and 2, a lancet injector 10 is shown including an elongate, generally cylindrical, housing 12 having a chamber or bore 14, and a lancet holder 16 slidable in the housing bore 14. Housing 12 has a proximal end 18 in which is secured an end plug 20, and a distal end 22 covered by a removable cap 24 having a central opening 25. Cap 24 is frictionally held in place by an annular bead 26 on the exterior of housing 12. In this way, the cap 24 can be snapped on and off the distal end 22 of the housing.
The lancet holder 16, as also seen in FIG. 3, includes a generally cylindrical portion or slide 28 having a lancet holding member 30 integrally connected to the distal end of the slide and a cylindrical extension or spring connector 32 at the proximal end of the slide. A spring 34, shown as a coil spring, is disposed in the bore 14 between the holder 16 and the plug 20. Spring 34 is shown engaged between the holder and a lower end portion of the housing. The connector 32 is provided with a series of external integral bumps 36 disposed in a spiral arrangement for threadedly receiving and holding the upper or distal end of coil spring 34. The spring 34 is threaded onto connector 32 until the end of the spring engages an integral stop bump 38. The end plug 20 is shown provided with an integral extension or spring connector 40 having a spiral series of integral bumps 42 which threadedly receives and, as shown, holds the lower end of coil spring 34. The spring 34 is threaded onto connector 40 until the end of the spring engages an integral stop bump 44. If desired, the spring connectors 32 and 40 may be provided with suitable screw threads instead of the series of bumps or the ends of the spring 34 may be fixed to those connectors by other suitable means.
The slide 28 has a hole 46 in which is secured a manual slide control member or control latch 48 which extends through a slot, indicated generally at 50, in the sidewall of the housing 12. Latch 48 extends to the exterior of the housing so that it provides an exterior manual control movable along the slot 50 for positioning the lancet holder 16 in a number of positions, as will be further described.
In assembling the device 10, the opposite ends of spring 34 may be respectively threaded onto connectors 32 and 40 to provide unitary assembly, as seen in FIG. 3. This assembly can be inserted into the proximal end of the housing 12. The free length of the spring 34 is such that the unit may be manually rotated in the housing 12 by rotating plug 20 until the hole 46 appears in the slot 50. The latch 48 may then be inserted through the slot and into hole 46. The latch 48 is fixed in the hole 46, for example, it may be adhesively connected or solvent bonded to the sidewalls of hole 46.
The holder 16 and connected latch 48 are preferably spring biased in a counterclockwise direction of rotation, as viewed in the drawings, that is arcuately toward engagement with the left sidewall 52 of slot 50. This may be accomplished by providing the plug 20 and inner wall of the housing 12 at its proximal end with cooperating surfaces which permit insertion of the plug in a selected relative position with respect to slide 28. For example, as shown in FIG. 3, the plug 20 is provided with a plurality of flats 54 which register with a plurality of flats 56 (FIG. 2) on the inner sidewall of bore 14 at the proximal end 18. In this way, after the latch 48 is secured in hole 46, the plug 20 can be rotated counterclockwise so that the latch 48 engages a wall of slot 50, and then the plug 20 is further rotated in the same direction a slight amount relative to holder 16, and then the plug is inserted into the end 18 of the housing. Because of the cooperating flats 54 and 56, the plug cannot rotate and remains in its inserted position with the spring 34 resiliently biasing the holder 16 and latch 48 leftwardly or counterclockwise toward the left edge 52 of slot 50. The plug 20 may be adhesively connected such as by applying a suitable adhesive to the plug prior to insertion or a suitable solvent where the plug and housing materials can be solvent bonded.
The lancet holding member 30 is shown as a sleeve or cylindrical barrel having inner sidewalls 58 which frictionally engage outer peripheral surfaces of a lancet 60. The lancet 60 is shown including a base or handle 62, such as of plastic material, and a needle 64, such as a solid stainless steel pointed needle. The handle 62 may be molded about the needle so that the tip of the needle extends outwardly beyond the upper end 66 of the handle. In FIG. 4, the lancet 60 is shown including an integrally molded needle cap or sheath 68 covering the pointed needle tip. The connection between the sheath 68 and the handle 62 is fragile so that by twisting or rotating the sheath relative to the handle, and then pulling the sheath from the needle tip, the needle tip is exposed. The depth of the lancet holding member 30 is less than the length of the lancet handle 62 so that the upper portion, such as its upper one half, extends out of the holder and may be grasped, for example, between the thumb and finger, for inserting the lancet 60 into the holder 30 and for removing it after use. The bottom of the lancet bottoms on the bottom of the member 30 as shown in FIG. 2.
The slot 50, as best seen in FIGS. 1, 2 and 5, is shaped so as to have a relative wide portion at the proximal end of the slot through which the control member 48 can be moved. In FIGS. 1 and 2, the member 48 is shown in its retracted position which places holder 16, member 30, and lancet 60 in the retracted position with the needle tip wholly within the housing 12. The control member 48 is shown releasably latched in an axial recess 69 having a downward protrusion 70 for securely holding the lancet holder in the retracted position. When the lancet holder 30 is in the retracted position, the spring 34 is in compression and exerting maximum longitudinal or linear spring force on the holder 16 in the distal direction. Also, the holder 16 is held in recess 69 against the biasing force of spring 34.
When the control member 48 is manually unlatched from the retracted position (FIGS. 1 and 2), such as by moving it leftward over the protrusion 70 by applying pressure with a finger or thumb, the holder 16, due to the force of spring 34 and inertia, moves swiftly linearly or longitudinally and distally through housing bore 14 to a skin piercing position wherein the point of needle 64 extends through opening 25 in the end cap 24 and distally of the distal end of the housing as shown in phantom in FIG. 5. During this movement control member 48 moves along a slot portion 72. The holder 16 and lancet 60 are quickly linearly retracted to a neutral position, that is, with the point of needle 64 retracted or withdrawn from the incision and within the housing 12 as shown in FIG. 5. Spring 34 is sized relative to housing 12 such that when the holder 16 and control member 48 are in this neutral position, the spring 34 is at its free length position or neutral force position, that is, spring 34 is substantially neither in tension nor compression.
In moving from the retracted position of FIG. 1 to the skin penetrating position shown in phantom in FIG. 5, it is primarily the inertia or momentum of the moving holder 16 that causes the lancet to move distally past the neutral position of the holder or free length position of the distal end of spring 34 (position shown in full in FIG. 5). Since the distal end of spring is extended distally beyond the position it would have when the spring 34 in its neutral or free length condition due primarily to the inertia of the moving holder 16, the spring is tensioned and therefore swiftly retracts or moves the needle point proximally from the piercing position back to the neutral position.
The parts may be proportioned such that the extent of distal travel of the lancet 60 may be limited by the engagement of the control member 48 with a sidewall 74 (FIGS. 1, 5 and 6) of the slot 50, the indicated phantom position of member 48 in FIG. 5, or, if desired, by the engagement of the upper end 66 of the lancet handle with the inner side of the end wall of cap 24. In some cases, the construction may allow the end 66 to strike the skin.
The holder 16 and lancet holder 30 may be moved to a lancet access or unloading and loading position, the position shown in FIG. 6. This is accomplished by removing cap 24 and urging the control member 48 rightwardly against the bias force from its neutral position of FIG. 5 and into an elongate slot portion 76 of slot 50, then longitudinally or linearly upwardly and distally into an enlarged slot portion 78, and then leftwardly into the access position in a recess 80 in slot 50 and which has a distally extending sidewall 82 holding the member 48 in place. During this distal movement in slot portion 76 the coil spring 34 is tensioned, that is, stretched beyond its neutral or free length condition of FIG. 5. The tensioned spring 34 tends to maintain the member 48 urged downwardly in groove 80 so that it cannot move out of the groove.
In the lancet access condition of holder 16, as shown in FIG. 6, the lancet holding member 30 extends through and above the upper or distal open end of the housing 12. In this position the upper portion of the lancet 60 may be grasped by the handle 62 and pulled upwardly to remove it from the member 30. A new lancet may then be inserted into the holder 30 until it bottoms against the inner bottom wall of the member 30. After a new lancet is inserted into the holding member in the access position of FIG. 6, the needle sheath such as sheath 68 (FIG. 4) is removed to expose the pointed needle tip, and then the external control member 48 is manually moved out of recess 80 into the enlarged slot portion 78. The member 48 is moved rightwardly against the rotary bias force of spring 34 into an elongate slot 76 where the force of tensioned spring 34 swiftly moves the slide 28 proximally longitudinally or axially of the housing so that it moves back into its neutral position shown in FIG. 5, the bias force of the spring urging it against the left edge 52 of the slot 50. The cap 24 may then be snapped back onto the distal end of housing 12.
In use, a new lancet, such as lancet 60, is inserted into the lancet holder 30 when the control member 48 is positioned in the lancet access position indicated in FIG. 6. The needle sheath, such as sheath 68 (FIG. 4) is removed from the lancet, and the control member 48 is manually moved out of recess 80 so that the tensioned spring 34 withdraws the lancet and slide 48 through slot portion 76 to the neutral position indicated in FIG. 5. The cap 24 or a new cap may now be placed over the distal end of the housing 12.
Next, the control member 48 is manually moved proximally or downwardly in slot portion 72 compressing coil spring 34 and then over to recess 68 to place the member 48 and holder 16 in a latched retracted or cocked position as shown in FIGS. 1 and 2. The housing 12 may now be hand grasped and the end cap 24 pressed against the skin, such as the skin of the finger, of the person whose blood is to be tested. The control member 48 may now be forced out or the retracted position so that the force of spring 34 and the inertia of the lancet 60 and lancet holder 16 effect piercing of the skin by the needle tip of the lancet and quick removal of the needle from the skin incision to the neutral position as indicated in FIG. 5. The cap 24 may now be removed and the control member 48 moved to the lancet access position as shown in FIG. 6 so that the used lancet may be easily and safely removed from the injector 10 and discarded. At this time, a new lancet may be inserted into the holding member 30 and the control member again moved to the neutral position of FIG. 5 so that the device is again ready to be used to effect skin piercing.
The blood flow caused by the lancet piercing the skin may be collected in a capillary tube or pipette and subjected to clinical testing. For example, at times, glucose testing may be done relatively often in the case of diabetics. Also, such testing may be self-performed such as in the home for monitoring blood glucose.
The lancet injector device 10 effects a very quick incision and withdrawal of the lancet needle so that patient discomfort is minimized. Since the lancet is substantially hidden by the housing, one does not see the lancet point during use and the anxiety of the patient is generally substantially less than where one sees the lancet point. Also, the injector 10 is easy to operate.
The injector 10 requires only one functional spring while operating in a simple and highly effective manner. The spring 34 is shown as a single coil propulsion compression spring which propels the lancet holder 16 for the skin piercing operation. Spring 34 provides the force for piercing the skin as well as swiftly withdrawing the lancet from the incision. The spring 34 is also tensioned when the device is in its lancet access position (FIG. 6) so that its force is also used to quickly withdraw the exposed lancet needle to the neutral position (FIG. 5) when the control member 48 is moved accordingly. Also, spring 34 provides the arcuate biasing force normally urging the slide 48 leftwardly when such bias is employed in the device. The construction of device 10 requires few moving parts and, in general, is simple and economical to make and use.
The housing 12, holder 16 and plug 20 may be economically molded from any suitable plastic, for example, from a copolymer made from acrylonitrile, butadiene, and styrene (ABS), or polypropylene. The cap 24 may also be made from a suitable plastic such as polypropylene. While a snap-on type cap 24 is shown, other cap constructions allowing attachment and removal are possible."
A problem with the lancet injectors of the two above-referenced patents is that the lancet tip must be manually removed from the lancet holder 30 after the lancet has been retracted from the skin of the subject. During this removal process, the lancet tip is exposed and in close proximity to the fingers of the person removing the lancet tip. This increases the possibility that the person removing the lancet may become inadvertently stuck by the lancet tip. In addition to the dangers inherent in puncture wounds, there is the additional danger that the person removing the lancet tip may become infected with a blood borne disease transmitted through the stick from a contaminated lancet tip. These are of course problems to be avoided.